This project involves the design and construction of more than 5 miles of a new elevated guideway between the Middle Street Transit Center Station and Aloha Stadium in Hawaii. The team is also responsible for the construction of the Pearl Harbor Naval Base transit station, two new stations near the Honolulu International Airport and the Middle Street station. This contract marks the third guideway project and part of HART’s plan to build a 20-mile passenger-rail system in Honolulu. The four stations that will be located within this section include Pearl Harbor Naval Base (PHNB) Station, Honolulu International Airport (HIA) Station, Lagoon Drive Station, and Middle Street Transit Center Station.
Legacy Foundations (a division of Shimmick) managed the drilled shaft and shoring installation for this project which includes 227 large diameters drilled shafts and over 100 small diameter shafts with reaching depths average of 200 to 300 feet; with the deepest reaching 350 feet. Shafts sizes ranged from two foot to twelve foot in diameter. Most shafts were temporarily cased using an oscillator or rotator. During the course of the project, there were multiple daily drilling shifts and up to four individual drillings spreads working to ensure the foundations stayed ahead of schedule.
The Airport Guideway and Stations segment included the largest CIDH ever installed, a 10ft. diameter drilled shaft reaching 357ft in depth. The drilled shaft was installed, while spanning a river, working off a temporary work trestle. The trestles were specifically engineered to carry the heavy drill rig loads, rebar and permanent casing weight. Crews installed 572,800 pounds of working casing to bottom of pile elevation using a 3.6m casing oscillator.
Crews worked day and night to excavate and connect casing to continue the removal of almost 1,000 cubic yards of mostly clay material. Upon completion, the shaft was cleaned and bottom tested, passing the very strict, less-than-half-inch settlement specification requirement for an end-bearing shaft. The 340-foot reinforcement cage, weighing 195,000 pounds, was built in six sections, spliced together over the excavated pile, and lowered in as completed.
This milestone was completed by tremie placing roughly 900 cubic yards of concrete with 365 feet of tremie pipe in five hours. Two concrete pumps were used to ensure adequate head pressure of the concrete could displace the water due to the extreme depth of this pile.